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Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians^1,2,3

¹ From the Central Laboratory, Department of Clinical Chemistry, Saarland University Hospital, Homburg, Germany.

Background: Vegetarians have a lower intake of vitamin B-12 than do omnivores. Early and reliable diagnosis of vitamin B-12 deficiency is very important.

Objective: The objective was to investigate vitamin B-12 status in vegetarians and nonvegetarians.

Design: The study cohort included 66 lactovegetarians or lactoovovegetarians (LV-LOV group), 29 vegans, and 79 omnivores. Total vitamin B-12, methylmalonic acid, holotranscobalamin II, and total homocysteine concentrations were assayed in serum.

Results: Of the 3 groups, the vegans had the lowest vitamin B-12 status. In subjects who did not consume vitamins, low holotranscobalamin II (< 35 pmol/L) was found in 11% of the omnivores, 77% of the LV-LOV group, and 92% of the vegans. Elevated methylmalonic acid (> 271 nmol/L) was found in 5% of the omnivores, 68% of the LV-LOV group, and 83% of the vegans. Hyperhomocysteinemia (> 12 µmol/L) was present in 16% of the omnivores, 38% of the LV-LOV group, and 67% of the vegans. The correlation between holotranscobalamin II and vitamin B-12 was weak in the low serum vitamin B-12 range (r = 0.403) and strong in the high serum vitamin B-12 range (r = 0.769). Holotranscobalamin II concentration was the main determinant of total homocysteine concentration in the vegetarians (ß = -0.237, P < 0.001). Vitamin B-12 deficiency led to hyperhomocysteinemia that was not probable in the upper folate range (> 42.0 nmol/L).

Conclusions: Vegan subjects and, to a lesser degree, subjects in the LV-LOV group had metabolic features indicating vitamin B-12 deficiency that led to a substantial increase in total homocysteine concentrations. Vitamin B-12 status should be monitored in vegetarians. Health aspects of vegetarianism should be considered in the light of possible damaging effects arising from vitamin B-12 deficiency and hyperhomocysteinemia.

Key Words: Vitamin B-12 • homocysteine • methylmalonic acid • holotranscobalamin • vegetarians

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Vegetarianism and vitamin B-12 (cobalamin) deficiency

Asok C Antony
AJCN 2003 78: 3-6. [Full Text]  

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